what's new with async await?

What's New with Async Await?

At WWDC 2024, several sessions covered updates and enhancements to the async and await features in Swift. Here are some key points:

1. Concurrency Model:

   • Swift uses the async and await syntax to model task suspension in code. A function that may suspend is marked with the async keyword, and the await keyword is used to indicate that a suspension can occur on that line. This allows the CPU to be yielded to other tasks while waiting for an asynchronous operation to complete. (A Swift Tour: Explore Swift’s features and design)

2. Memory Management:

   • Async functions in Swift are implemented in a way that keeps their local state on a separate stack from the C stack. They are split into multiple functions at runtime to handle potential suspension points. This design helps in managing memory more efficiently and ensures that async tasks hold onto one or more slabs of memory, which can be allocated and deallocated as needed. (Explore Swift performance)

3. Partial Functions:

   • When an async function is executed, it is split into partial functions that span the gaps between potential suspension points. This means that only one partial function is on the C stack at any given time, which helps in managing the function's state and memory more effectively. (Explore Swift performance)

4. Testing with Async Await:

   • In Swift testing, the await keyword works the same way as in production code, allowing tests to suspend and keep the CPU busy while work is pending. This helps in running tests in parallel and ensures that asynchronous conditions are handled efficiently. (Go further with Swift Testing)

5. Actors:

   • Swift introduces actors, which are reference types that encapsulate shared mutable state and automatically protect their state by serializing accesses. Calls to actor methods from outside the context of the actor are asynchronous, requiring the use of the await keyword. (A Swift Tour: Explore Swift’s features and design)

6. Migration to Swift 6:

   • When migrating to Swift 6, adopting concurrency features like async and await can help in managing delegate callbacks and ensuring that methods and property accesses are made on the main thread. This helps in maintaining data-race safety and improving the overall concurrency model of the application. (Migrate your app to Swift 6)

Relevant Sessions

• A Swift Tour: Explore Swift’s features and design
• Explore Swift performance
• Go further with Swift Testing
• Migrate your app to Swift 6

These sessions provide a comprehensive overview of the new features and improvements in Swift's concurrency model, particularly focusing on async and await.